#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
#include "syscall.h"

// User code makes a system call with INT T_SYSCALL.
// System call number in %eax.
// Arguments on the stack, from the user call to the C
// library system call function. The saved user %esp points
// to a saved program counter, and then the first argument.

// Fetch the int at addr from the current process.
int fetchint(uint addr, int *ip)
{
	if (addr >= proc->sz || addr + 4 > proc->sz)
		return -1;
	*ip = *(int *)(addr);
	return 0;
}

// Fetch the nul-terminated string at addr from the current process.
// Doesn't actually copy the string - just sets *pp to point at it.
// Returns length of string, not including nul.
int fetchstr(uint addr, char **pp)
{
	char *s, *ep;

	if (addr >= proc->sz)
		return -1;
	*pp = (char *)addr;
	ep = (char *)proc->sz;
	for (s = *pp; s < ep; s++)
		if (*s == 0)
			return s - *pp;
	return -1;
}

// Fetch the nth 32-bit system call argument.
int argint(int n, int *ip)
{
	return fetchint(proc->tf->esp + 4 + 4 * n, ip);
}

// Fetch the nth word-sized system call argument as a pointer
// to a block of memory of size n bytes.  Check that the pointer
// lies within the process address space.
int argptr(int n, char **pp, int size)
{
	int i;

	if (argint(n, &i) < 0)
		return -1;
	if ((uint)i >= proc->sz || (uint)i + size > proc->sz)
		return -1;
	*pp = (char *)i;
	return 0;
}

// Fetch the nth word-sized system call argument as a string pointer.
// Check that the pointer is valid and the string is nul-terminated.
// (There is no shared writable memory, so the string can't change
// between this check and being used by the kernel.)
int argstr(int n, char **pp)
{
	int addr;
	if (argint(n, &addr) < 0)
		return -1;
	return fetchstr(addr, pp);
}

extern int sys_chdir(void);
extern int sys_close(void);
extern int sys_dup(void);
extern int sys_exec(void);
extern int sys_exit(void);
extern int sys_fork(void);
extern int sys_fstat(void);
extern int sys_getpid(void);
extern int sys_kill(void);
extern int sys_link(void);
extern int sys_mkdir(void);
extern int sys_mknod(void);
extern int sys_open(void);
extern int sys_pipe(void);
extern int sys_read(void);
extern int sys_sbrk(void);
extern int sys_sleep(void);
extern int sys_unlink(void);
extern int sys_wait(void);
extern int sys_write(void);
extern int sys_uptime(void);
extern int sys_shutdown(void);
extern int sys_forkwinner(void);
extern int sys_alloc_sem(void);
extern int sys_wait_sem(void);
extern int sys_signal_sem(void);
extern int sys_dealloc_sem(void);
extern int sys_enable_schedule_display(void);
extern int sys_set_priority(void); 

static int (*syscalls[])(void) =
{
	[SYS_fork] sys_fork,	[SYS_exit] sys_exit,	[SYS_wait] sys_wait,
	[SYS_pipe] sys_pipe,	[SYS_read] sys_read,	[SYS_kill] sys_kill,
	[SYS_exec] sys_exec,	[SYS_fstat] sys_fstat,	[SYS_chdir] sys_chdir,
	[SYS_dup] sys_dup,		[SYS_getpid] sys_getpid,[SYS_sbrk] sys_sbrk,
	[SYS_sleep] sys_sleep,	[SYS_uptime] sys_uptime,[SYS_open] sys_open,
	[SYS_write] sys_write,	[SYS_mknod] sys_mknod,	[SYS_unlink] sys_unlink,
	[SYS_link] sys_link,	[SYS_mkdir] sys_mkdir,	[SYS_close] sys_close,
	[SYS_shutdown] sys_shutdown,[SYS_forkwinner]sys_forkwinner,
	[SYS_alloc_sem] sys_alloc_sem,	[SYS_wait_sem]sys_wait_sem,	[SYS_signal_sem]sys_signal_sem,	[SYS_dealloc_sem]sys_dealloc_sem,
	[SYS_enable_schedule_display]sys_enable_schedule_display,[SYS_set_priority]sys_set_priority
};

void syscall(void)
{
	int num;
	
	num = proc->tf->eax;
	if (num > 0 && num < NELEM(syscalls) && syscalls[num])
	{
		proc->tf->eax = syscalls[num]();
	}
	else
	{
		cprintf("%d %s: unknown sys call %d\n", proc->pid, proc->name, num);
		proc->tf->eax = -1;
	}
}
